Book excerpt: This book presents a compilation of selected papers from the Fourth International Symposium on Software Reliability, Industrial Safety, Cyber Security and Physical Protection of Nuclear Power Plant, held in August 2019 in Guiyang, China. The purpose of the symposium was to discuss inspection, testing, certification and research concerning the software and hardware of instrument and control (I&C) systems used at nuclear power plants (NPP), such as sensors, actuators and control systems. The event provides a venue for exchange among experts, scholars and nuclear power practitioners, as well as a platform for the combination of teaching and research at universities and enterprises to promote the safe development of nuclear power plants. Readers will find a wealth of valuable insights into achieving safer and more efficient instrumentation and control systems.